The major objective of this research project is to investigate the significance of interactions between fluoride and otherminerals under ordinary dietary conditions using the rat as an animal model. The mineral factors have been selected to reflect their chemical similarity to fluoride (Chloride, iodide) and because of their ability to form insoluble complexes with fluoride in the gastrointestinal tract (calcium, magnesium, iron, zinc, lead). Additional variables that may affect interactions between fluoride and other mineral factors are part of the experimental design including age and physiological state, levels and chemical form of mineral factors and chemical form of fluoride. Criteria of assessment include absorption, skeletal uptake and retention of fluoride in the weanling rat. Additional studies are to assess interactions between fluoride and other minerals during gestation and lactation with emphasis on offspring bone and tooth fluoride and caries resistance. Although data about interactions between fluoride and other minerals may appear to be considerable in the literature, the proposed research provides new information. Traditional fluoride balance studies have not been reported in most studies. In a series of much quoted studies, fluoride and mineral factors were administered as one dose by gastric intubation which cannot be considered to be ordinary dietary conditions. Interactions between fluoride and other minerals have also been largely confined to fluorosis rather than nutritional levels of fluoride. Studies that have investigated the ability of other elements to form insoluble complexes with fluoride used fluoride concentrations equal to fluoridated water and concentration of other elements that are typical of hard water. Since drinking water was considered to be the vehicle for fluoride that would reduce caries in children, the importance of insoluble fluoride complex formation with other minerals was dismissed. Recent evidence, however, has shown that foods prepared in fluoridated water can make a significant contribution to a young child's fluoride intake during the period of pernament teeth formation. These same foods also contain considerable amounts of major and trace elements compared to hard water which increases the potential for insoluble fluoride complex formation.